Insulation displacing barrel contact

Abstract: A barrel-shaped IDC contact (2) comprises a cylindrical body section (4) having a longitudinal IDC slot (5) formed by opposed edges (6). Extending longitudinally alongside the edges (6) are cutouts (10) forming a resilient beam section (12) therebetween in order to increase the resiliency of the IDC slot (5). The latter reduces degradation of the contact (2) by stress relaxation. The cutouts (10) also provide better access of plating fluids to the interior of the barrel thereby improving penetration thereof and allowing the plating line to run faster.

Description: This invention relates to an improved barrel-shaped insulation displacing contact (IDC) for making electrical contact to conducting wires. Barrel-shaped insulation displacing contacts are already known and shown for example in US-A-3 860 318, whereby such contacts procure a number of advantages with respect to other IDC designs such as ease of manufacturing, an improved ability to accommodate conductors of different sizes, and good mechanical and electrical properties. Additionally, barrel-shaped IDC's are well adapted to mass termination i.e. a plurality of conducting wires can be simultaneously connected to the plurality of barrel-shaped IDC's in a simple, reliable and cost-effective manner. FR-A-2 419 594 discloses an insulation displacing contact (IDC) with a body section having a cutout extending in the longitudinal direction of the IDC. A second cutout is also provided, each of the cutouts being proximate a corresponding opposed IDC edge, each cutout having a completely closed peripheral edge. US-A-4 343 529 discloses an improved terminal block in which each terminal is barrel-shaped with the flared skirt which locks the terminal from movement in one direction, and a plate portion of the terminal is bent over to lock the terminal from movement in an opposite direction. The plate cooperates with projecting ears of the terminal to prevent rotation. In order to further improve the reliability and the cost-effectiveness of barrel-shaped IDC contacts, it would be desirable to increase the flexibility of the contacting edges of the IDC slots, in particular to decrease degradation of the contact pressure between the conducting wire and edges of the IDC slots caused by stress relaxation. Stress relaxation is caused by creep which is a permanent material displacement, the rate of which isa function of the temperature and stress within the material. By increasing the flexibility of the IDC contacts, stress within the contact is reduced, therefore reducing stress relaxation. In order to reduce the manufacturing cost, it would also be desirable to provide good access, during the plating procedure, to the inside of the barrel contact as the plating procedure can then be accelerated. the functional contact surfaces of IDC's i.e. the contact edges, are commonly plated in order to reduce contact corrosion which increases the electrical resistance between the conducting wire and IDC terminal, whereby not only the actual contact edge must be plated but also the surrounding surfaces as the corrosion "overflows". The latter is also to ensure that a sufficient plating thickness is achieved, to avoid excessive porosity of the plating layer. It is therefore an object of this invention to provide a barrel-shaped insulation displacing contact that has improved stress relaxation characteristics. It is a further object of this invention to provide a barrel-shaped insulation displacing contact with reduced manufacturing time. It is a further object of this invention to provide a cost-effective and reliable insulation displacing contact. The objects of this invention have been achieved by providing a barrel-shaped insulation displacing contact (IDC) stamped and formed from sheet metal and comprising a barrel-shaped body section extending longitudinally between a wire receiving end and a terminal end, the body section comprising a longitudinally disposed IDC slot formed by a pair of spaced-apart opposed IDC edges of a seam of the body section arising from folding together thereof from the sheet metal, where the IDC slot extends divergingly into a wire entry section which extends to the wire receiving end, characterized in that at least one cutout is provided in the body section proximate one of the opposed edges and alongside the wire entry section to form a resilient beam and a resilient member respectively therebetween. The preferred embodiment of this invention will now be described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is a perspective view of a barrel-shaped insulation displacing contact (IDC) according to this invention. Referring to Figure 1, an insulation displacing contact 2 is shown comprising a longitudinally disposed, substantially cylindrical body section 4 extending between a wire receiving end 9 and a terminal end 7, the contact 2 stamped and formed from sheet metal, the body section folded together from the sheet metal base so that it's seam forms a longitudinal IDC slot 5 having opposed IDC edges 6 extending into a Y-shaped diverging entry section 8 that ends at the wire receiving end 9 of the contact 2. From the terminal end 7, extends a terminal section (3) (only partially shown) for mating to a complementary conductor (not shown). The body section 4 is provided with longitudinally disposed oblong cutouts 10 alongside and spaced from the opposed IDC edges 6 such that a flexible beam member 12 is formed therebetween. Further cutouts 14 are provided between the first cutouts 10 and the terminal body end 7. Both the cutouts 10 and 14 have fully closed peripheral edges 11, 15 respectively. The cutouts 10 increase the flexibility of the IDC slot 5 with respect to a conducting wire stuffed between the opposed IDC edges 6 adjacent the beams 12, due to the resiliency not only of the barrel-shaped body section 4 which bends open, but also the resilient bending of the beams 12. Due to the greater flexibility, stresses within the body section 4 are well distributed, enabling the body section 4 to contain more elastic energy whilst decreasing stress relaxation due to creep when comparing to a barrel-shaped IDC contact not comprising the cutouts 10 and resilient beam section 12. The cutouts 10 extend longitudinally beyond the opposed IDC edges 6 and alongside the Y-shaped entry section 8 in order to increase the flexibility of the IDC slot 5 during stuffing of the wire therein so as to avoid having excessive pressure on the conducting strands of the wire during entry into the IDC slot opposed edges 6. Excessive pressure could damage the conducting strands by cutting thereinto, thereby reducing the contact pressure between the edges 6 and conducting strands once fully inserted. The holes 10 and 14 also have the functional reducing manufacturing costs by allowing a more efficient penetration and distribution of the plating inside the body section 4. During the plating procedure a plurality of IDC contacts 2 are joined together via a carrier strip and run through various plating baths in a continuous line process. The speed of this process is determined, inter alia by the time during which the contact 2 must remain immersed in the plating baths in order to have sufficient deposit of the plating metal concerned (for example nickel) on the functional zones of the contact. In order to avoid corrosion "overflowing" onto the contact zones, plating must be deposited not only on, but also around the opposed IDC edges 6 of the slot 5. This means that not only the outer surface of the barrel body section 4 but also the inner surface requires controlled and sufficient plating of the plating metal(s). The holes 10 and 14 improve the quality of plating inside the barrel-shaped body section 4 and also increase the plating speed due to the more efficient penetration and greater flow of the electrolytic plating fluid therein. Advantageously therefore, the cutouts alongside the IDC slot 5 in the barrel-shaped contacts 2 provide firstly for a more cost-effective terminal due to the reduced time required for plating, and secondly for a more reliable contact with less risk of degradation caused by stress relaxation.

Claims: A barrel-shaped insulation displacing contact (IDC) (2) stamped and formed from sheet metal and comprising a barrel-shaped body section (4) extending longitudinally between a wire receiving end (9) and a terminal end (7), the body section (4) comprising a longitudinally disposed IDC slot (5) formed by a pair of spaced-apart opposed IDC edges (6) of a seam of the body section arising from folding together thereof from the sheet metal, where the IDC slot (5) extends divergingly into a wire entry section (8) which extends to the wire receiving end (9), characterized in that at least one cutout (10) is provided in the body section (4) proximate one of the opposed edges (6) and alongside the wire entry section (8) to form a resilient beam (12) and a resilient member (13) respectively therebetween. The contact (2) of claim 1 characterized in that the cutout (10) has an oblong shape extending substantially in the longitudinal direction. The contact of any preceding claim characterized in that there are further cutouts (14) in the body section (4) disposed between the cutouts (10) and the terminal end (7). The contact of any preceding claim characterized in that there are a pair of the cutouts (10), each proximate a corresponding opposed IDC edge (6). The contact of any preceding claim characterized in that the at least one cutout (10) has a completely closed peripheral edge (11). The contact of claim 3, characterized in that there are a pair of the further cutouts (14).

Inventors: MARTINS CRISOSTOMO, MARTINS, CRISOSTOMO
Applicants: WHITAKER CORP, THE WHITAKER CORPORATION
Application year: 1994
Main classification: H01R4
IPC codes: H01R4